1. Field of the Invention
This invention relates to a snap zipper and a bag with the snap zipper, which is used as a bag for foods, medical supplies or the like.
2. Description of the Related Art
A bag (a bag with a snap zipper), which is sealable by a band-shaped snap zipper, composed of a snap-zipper male member and a snap-zipper female member and located at an opening area of the bag, is used in various fields, such as foods, medical supplies, miscellaneous goods and so on. Various methods for fabricating the bag with the snap zipper are proposed.
For instances, (1) a method in which a bag body film and a snap zipper are unitedly formed by an extrusion molding method; (2) a method in which a snap zipper is formed on a bag body film by an extrusion molding method; (3) a method in which a tape previously formed with a snap zipper is fused on a bag body film; and so on.
Lately, method (3) has been widely used in view of the production cost, stock material and so on.
Generally, the material of the snap zipper is a resin of a similar type to a sealant layer as a film layer to which the snap zipper of the bag body is fused thereon. For example, where the sealant layer is polypropylene, the snap zipper is formed from the same polypropylene.
The conventional snap zipper consisting of polypropylene has inferior properties for cold proofing because of a high-rigidity, so that it can be broken at a low temperature in winter when the engaging strength of a male member and a female member is enhanced.
Further, when the bag is made by fusing the snap zipper on a laminated film composed of a biaxial oriented polypropylene film and a non-oriented polypropylene film, the melting points of the snap zipper and the laminated film are similar, resulting in a disadvantage where a fused area between the snap zipper and the biaxial oriented polypropylene film forming the outer-most layer of the bag is easily heat-deteriorated. The heat deterioration especially occurs easily in the process in which an area of the snap zipper, located at the side-sealed portion of the bag body, is heatedly pressured (i.e., crushing of zipper) after the snap zipper is fused onto the laminated film. Therefore, a high degree of art for producing the bag is required in order to avoid the heat deterioration.
It is the object of the present invention to produce a snap zipper and a bag with a snap zipper, in which the cold proofing is improved, and the snap zipper is easily fused on a bag body without heat deterioration.